Such a piano has been proposed which has an electronic sound source combined with acoustic piano. This realizes performance using the electronic sound source as well as normal piano play.
In the stated kind of piano it is known to provide a mechanism which prevents the action caused by key depression from being transmitted to hammers such that normal play sound that would be otherwise created by striking strings (hereinafter referred to as string striking-sound) is eliminated during performance using electronic sound source. Thus, string striking-sound is not generated during the performance using electronic sound source.
During the performance using electronic sound source, stepped shutters and first and second key sensors, provided below keys and on the main body of a piano, respectively, serve as detection means for detecting actions related to key depression and key release. The first and second key sensors are comprised of a pair of a light emitting element and light receiving element. When there is a blockage between these elements, on-signal is generated. When a key is depressed, the stepped shutter first eclipses the light path of the first key sensor, and then, with a specified interval of time, eclipses the light path of the second key sensor. The timing and the time lag of such light path blockage at the first and second key sensors are detected by control means operating to control electronic sound source. The control means then prepares, according to control program, performance data in the form of control signal and sends it to the electronic sound source. Consequently, play sound is generated at the electronic sound source.
According to the described prior art, the output of the performance data by the control means toward the electronic sound source is simultaneous to the on-signal at the second key sensor. Therefore, once the light path is blocked at the second key sensor, sound goes off immediately after at the electronic sound source.
However, the string striking-sound generated when the piano is played as a normal piano is caused by the kinetic energy of key depression which is transmitted to a hammer and causes it to strike a string. Since such process takes a substantial time period, there is a difference between the sound emission, or note-on, timing of the string striking-sound during normal piano play and that of the sound generated at the electronic sound source, thereby leading to an imbalance of created performance as a whole between the normal piano play and a play using electronic sound source. As a result, a player feels awkward when he plays using one of the sound source after using the other sound source.